Disease control important part of wheat production

What is in this article?:

• Whenever a new wheat variety is released, it is usually resistant to the most commonly occurring races of the fungi that is prevalent at the time, and the race population can change quickly.

• While heaviest disease-related losses occur in the Midwest, damaging scab outbreaks are seen in Alabama wheat, primarily in the state’s Tennessee Valley region.

Planting disease-resistant varieties remains the most effective and economical way to control diseases in wheat, with resistance being the primary means of managing yield-robbing foliar diseases.

However, few recommended varieties have “good” or “high” resistance to all major foliar diseases, and the fungi that cause leaf rust and powdery mildew are constantly changing. Whenever a new variety is released, it is usually resistant to the most commonly occurring races of the fungi that is prevalent at the time, and the race population can change quickly.

Weather conditions during the winter and spring are one of several factors that affect the severity of wheat diseases. If the winter and spring are cool and/or dry, leaf diseases usually will be of little or no significance regardless of a variety’s resistance. A warm, wet winter and spring are favorable for infection by disease-causing fungi.

The combination of low resistance and warmer than normal winters and springs are favorable for severe powdery mildew, leaf rust, and Stagonospora nodorum leaf and glume blotch, three of the most important fungal diseases.

Seedborne and soilborne diseases are controlled primarily by seed treatments and crop rotation.

One of the more increasingly important and damaging diseases of wheat in the United States is scab or Fusarium head blight. While heaviest disease-related losses occur in the Midwest, damaging scab outbreaks are seen in Alabama wheat, primarily in the state’s Tennessee Valley region, says Austin Hagan, Auburn University Extension plant pathologist.

“Losses are not only due to sizable reductions in the germination, numbers, and test weight of seed from scab-blighted heads, but also to the production of mycotoxins by the causal fungus in diseased seed,” says Hagan. “Other cereal hosts of these causal fungi are barley, corn and grain sorghum. Given favorable weather patterns, wheat drilled behind no-till corn is at highest risk for a destructive scab outbreak.”

Moist weather patterns during flowering through early kernel fill are required for scab development, he adds. Severe scab outbreaks are likely when three to more rain or irrigation events occur from the start of flowering (anthesis) through three to five days post-bloom, particularly on the scab-susceptible wheat varieties grown in Alabama, says Hagan.